Baclofen intravenous solution 2 mg/mL will be manufactured and provided by Allaysis, LLC. Prism Clinical Research will purchase oral baclofen tablets (10 mg) from a commercial supplier. Subject will start baclofen at a 5 mg oral dose every 8 hours. Oral baclofen will be increased incrementally and self-administered over 13 days to a maximum dose of 20 mg every 8 hours. Subjects will be crossed over to 16 mg intravenous baclofen infused over 120 (n=6) or 150 (n=6) minutes every 8 hours for 11 doses. Subjects will be changed back to oral baclofen at a 15 mg dose self-administered every 8 hours and tapered off of baclofen over 15 days. Following the completion of this group of 12 subjects, the remaining 30 subjects will receive IV baclofen at the infusion duration that best meets the criteria for bioequivalence.